The present invention relates to a method for attaching a cable for communication optical fibers, etc., which are dragged into pipes such as sewage pipes made of resin, and a cable holder used for the method.
Optical fibers for communications that are able to transmit a great deal of information at high accuracy without being influenced by electric hindrance have recently spread as communication networks in line with quick advancement of information society. There are many cases where such communication networks are laid in the existing sewage pipes in the case of city zones. Where optical fibers for communications are laid in sewage pipes, cables consisting of optical fibers are usually attached to the ceiling of a sewage pipe by cable holders so that a water flow is not hindered due to foreign substances being adhered thereto and being accumulated therein.
As such a method for attaching a cable, some methods have been publicly known, one of which is, as disclosed by Japanese Patent Publication No. Hei-3-50483, a method for attaching a cable, wherein a drilling device incorporated in a work carriage traveling in a pipe such as a sewage pipe drills a pair of holes on the inner wall of the pipe, the legs of a roughly U-shaped cable holder are driven into the respective holes by a driving device incorporated in the work carriage after the cable is grasped by the cable holder, another of which is, as disclosed by Japanese Unexamined Patent Publication No. 8-103012, a method in which, by using a cable holder having a laterally faced hook-shaped cable retainer at its upper and lower parts thereof, after the cable holder-attached portion is pushed, by a drilling device, in the holes drilled in the inner wall of a pipe and is adhered thereinto, the cable is grasped by a cable catcher of a subsequently coming work carriage and the cable is caught in the cable retaining portion, and the other of which is, as disclosed by Japanese Unexamined Patent Publication Nos. 2000-261924 and 2001-28819, a method having a cable for attaching a cable, which is caught by a cable catcher incorporated in a work carriage traveling in a pipe, by pushing the same in a cable holder retaining portion which has a cable retaining portion and fixes the upper attaching portion thereof by screwing or burying the upper attached portion in the inner wall of the pipe, wherein the cable retaining portion has such a section having an inlet opening facing downward, in which a pot is turned upside down. In addition, Japanese Unexamined Patent Publication No. Hei-10-66238 disclosed a method in which, as a cable holder to be attached to a resin pipe such as a vinyl chloride pipe, etc., an attaching portion is driven in the resin pipe while being heated by supplying an electric current, wherein the attaching portion is deposited and fixed thereat.
Wherein the pipe is a resin pipe such as a vinyl chloride pipe, etc., it is difficult to drill holes by a drilling device in comparison with ceramic pipes or Hume pipes, wherein there is a fear that such a resin pipe is damaged or broken when drilling by the drilling device. However, if the attaching portion is heated, deposited and fixed in a resin pipe, the above-described problem does not occur. But, the method for attaching a cable as shown in Japanese Unexamined Patent Publication No. Hei-10-66238 is constructed so that the attaching portion is heated and is driven into a resin pipe, and the attaching portion is deposited and fixed in a position. Therefore, if the performance guarantee temperature of cables is comparatively low to be 60xc2x0 C. as in optical fibers, the cable may be subjected to thermal influences and the temperature thereof may exceed its performance guarantee level when heating the attaching portion for fixing.
It is therefore an object of the invention to provide a method for attaching a cable, by which the cable is not subjected to any thermal influence when depositing and fixing a cable holder in a resin pipe.
The method according to the invention is composed so that a cable holder is heated to be deposited and fixed in the inner wall of a resin pipe and, after the cable holder is deposited, fixed and cooled down, a cable is caught by the cable holder, and the method comprises the steps of dragging a cable such as optical fibers for communications into a pipe such as a sewage pipe, etc., which is made of resin such as vinyl chloride, polyester, etc., pressure-fitting, depositing and fixing the attaching portion of a metal-made cable holder on the inner wall of the pipe by heating the attaching portion thereof by a heating means, and engaging the cable passed through the pipe with cable holders after the cable holders deposited and fixed on the inner wall of the pipe are cooled down.
According to the invention, since the cable is engaged with the cable holders after the cable holders are deposited and fixed on the inner wall of a resin pipe and cooled down, the cable is not subjected to any thermal influence.
With the invention, the step of dragging a cable into a pipe such as a sewage pipe may be carried out before or after the step of depositing and fixing the cable holder on the inner wall of the pipe.
A cable holder used for the invention may consist of, for example, an attaching portion 32 having a laterally-faced hook-like part 31 as shown in FIG. 13. Such a type may be employed, in which, after the tip end of the attaching portion is pressure-fitted into a resin pipe 33 and deposited and fixed therein, a cable 34 is pushed in between the inner wall of the resin pipe and the tip end of the hook-like part, and is caught in the hook-like part 31. However, preferably, as shown in FIG. 14, such a type may be employed, in which the hook-like part is just like an inverted pot that has an narrowed inlet opening 36 at its downward side, and after an attaching part 37 projecting upward is pressure-fitted into a resin pipe 38 and deposited and fixed therein, the cable 34 is pushed in from below through the inlet opening for engagement.
In the latter cable holder as shown in FIG. 14, it will become possible to raise the retaining position of the cable 34 and attach the cable 34 in contact with the inner wall of a pipe by strongly pressure-fitting the attaching portion 37 to a resin pipe 38. In the case of a sewage pipe, the clearance between the cable 34 and the inner wall of the pipe can be removed, wherein it is possible to prevent hair and foreign substances contained in filthy water from being accumulated therein.
It is another object of the invention to provide a cable holder, which can be easily pressure-fitted into a resin pipe, and can be securely attached thereto.
A cable holder according to the present invention includes a cable retaining portion with which a cable is engaged, and a claw protruding upward from the cable retaining portion. When attaching the cable holder on a sewage pipe made of resin, the claw is heated by a heating means such as a heater, and is pressure-fitted into the inner wall of the pipe to be deposited and fixed thereon. After that, a cable such as an optical fiber, which is dragged into the pipe such as a sewage pipe is pushed in the cable retaining portion and is engaged therewith.
According to the invention, since the portion to be inserted into the resin pipe is made into a claw, it becomes possible to facilitate the pressure-fitting thereof into the resin pipe.
The above-described claw may be single, but it may be preferably plural. If a plurality of claws are provided, the attaching of the cable holder on the resin pipe can be further stabilized.
Where a plurality of claws are provided, the respective claws may be juxtaposed with a fixed interval in the circumferential direction of the resin pipe. But they are preferably arranged with a fixed interval toward the axial direction of the resin pipe.
In the former case, if the claws are pressure-fitted into the resin pipe in a state where the cable holder is inclined in the left or right direction, a claw at either left or right may be deeply inserted into the resin pipe, and the others are shallowly inserted thereinto, wherein the attaching thereof will not be stabilized. To the contrary, in the latter case, even if the claws are pressure-fitted into the resin pipe in a state where the cable holder is inclined left or right, the claws that are arranged toward the axial direction of a pipe can be inserted into the resin pipe at a uniform depth.
Also, in the present invention, due to the above-described reason, such a type may be used, in which the shape of the cable retaining portion is just like the section of an inverted pot that has a narrowed inlet opening at its downward side, as shown in FIG. 14.
The other objects and advantages of the invention will be made more apparent based on the following description of embodiments thereof with reference to the accompanying drawings.